Narrative:

We had been cleared directly to dagett then via the skebr RNAV one arrival, cross misen at FL240. We then thought we were cleared to cross clarr at 13000 ft and cleared for the skebr one arrival. We were encountering constant light to moderate turbulence all the way down. I had actually secured the cabin at 13000 ft. It had been bumpy the whole flight. Upon making the turn at skebr we reviewed the next altitude on the chart and in the legs page. We then set and confirmed 12000 ft for the cross altitude at ipumy. During the descent to 12000 ft we were issued additional low level traffic, with no further comment from approach control. After leveling at 12000 ft we were just over kepec. Approach control asked us if we had been cleared to 12000 ft or if we had descended on our own. We replied with 'we believe we were cleared for the arrival' after the 13000 ft at clarr. We were asked to call the supervisor. I talked to the supervisor for about 30 mins, with regards to the fact that we had been in and out of las 6 times in the last 2 days. On each of the arrs we were given a different type of altitude clearance. We virtually had transposed the clearance from the previous arrival and both confirmed the next crossing altitude. We had been extra cautious about the airplane flying the correct arrival route since we missed the turn at skebr due to an LNAV fault, on our previous arrival the day before. An ir and as soon as possible were filed for that trip along with maintenance write-ups. The controller was unsure of what our clearance was and had called center for a review. Factors: 7 legs the day before, all in and out of las. Turbulence, short layover, a lot of traffic, concern over the previous deviation. The supervisor said they are really trying to work this out as they have over 20 deviations on the RNAV procedures. Callback conversation with reporter revealed the following information: reporter called the L-30 supervisor as requested to review their arrival scenario. At the time ZLA had not provided any information as to what clearance was issued to the crew. The reporter said he told the supervisor that his navigation failed as they crossed over skebr and that the controller provided radar vectors to the next fix. He said the same thing had happened the previous day and that he wrote it up for maintenance to check. He said he did not expect a callback from the L-30 supervisor.

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Original NASA ASRS Text

Title: INBOUND TO LAS, A B737-700 FLC RECEIVED CLRNC VIA THE SKEBR ARR FROM ZLA THAT IS LATER QUESTIONED BY LAS APCH CTL.

Narrative: WE HAD BEEN CLRED DIRECTLY TO DAGETT THEN VIA THE SKEBR RNAV ONE ARR, CROSS MISEN AT FL240. WE THEN THOUGHT WE WERE CLRED TO CROSS CLARR AT 13000 FT AND CLRED FOR THE SKEBR ONE ARR. WE WERE ENCOUNTERING CONSTANT LIGHT TO MODERATE TURB ALL THE WAY DOWN. I HAD ACTUALLY SECURED THE CABIN AT 13000 FT. IT HAD BEEN BUMPY THE WHOLE FLT. UPON MAKING THE TURN AT SKEBR WE REVIEWED THE NEXT ALT ON THE CHART AND IN THE LEGS PAGE. WE THEN SET AND CONFIRMED 12000 FT FOR THE CROSS ALT AT IPUMY. DURING THE DSCNT TO 12000 FT WE WERE ISSUED ADDITIONAL LOW LEVEL TFC, WITH NO FURTHER COMMENT FROM APCH CTL. AFTER LEVELING AT 12000 FT WE WERE JUST OVER KEPEC. APCH CTL ASKED US IF WE HAD BEEN CLRED TO 12000 FT OR IF WE HAD DSNDED ON OUR OWN. WE REPLIED WITH 'WE BELIEVE WE WERE CLRED FOR THE ARR' AFTER THE 13000 FT AT CLARR. WE WERE ASKED TO CALL THE SUPVR. I TALKED TO THE SUPVR FOR ABOUT 30 MINS, WITH REGARDS TO THE FACT THAT WE HAD BEEN IN AND OUT OF LAS 6 TIMES IN THE LAST 2 DAYS. ON EACH OF THE ARRS WE WERE GIVEN A DIFFERENT TYPE OF ALT CLRNC. WE VIRTUALLY HAD TRANSPOSED THE CLRNC FROM THE PREVIOUS ARR AND BOTH CONFIRMED THE NEXT XING ALT. WE HAD BEEN EXTRA CAUTIOUS ABOUT THE AIRPLANE FLYING THE CORRECT ARR RTE SINCE WE MISSED THE TURN AT SKEBR DUE TO AN LNAV FAULT, ON OUR PREVIOUS ARR THE DAY BEFORE. AN IR AND ASAP WERE FILED FOR THAT TRIP ALONG WITH MAINT WRITE-UPS. THE CTLR WAS UNSURE OF WHAT OUR CLRNC WAS AND HAD CALLED CTR FOR A REVIEW. FACTORS: 7 LEGS THE DAY BEFORE, ALL IN AND OUT OF LAS. TURB, SHORT LAYOVER, A LOT OF TFC, CONCERN OVER THE PREVIOUS DEV. THE SUPVR SAID THEY ARE REALLY TRYING TO WORK THIS OUT AS THEY HAVE OVER 20 DEVS ON THE RNAV PROCS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CALLED THE L-30 SUPVR AS REQUESTED TO REVIEW THEIR ARR SCENARIO. AT THE TIME ZLA HAD NOT PROVIDED ANY INFO AS TO WHAT CLRNC WAS ISSUED TO THE CREW. THE RPTR SAID HE TOLD THE SUPVR THAT HIS NAV FAILED AS THEY CROSSED OVER SKEBR AND THAT THE CTLR PROVIDED RADAR VECTORS TO THE NEXT FIX. HE SAID THE SAME THING HAD HAPPENED THE PREVIOUS DAY AND THAT HE WROTE IT UP FOR MAINT TO CHK. HE SAID HE DID NOT EXPECT A CALLBACK FROM THE L-30 SUPVR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.